The present invention relates to an apparatus and an associated method for hooping packing units. An apparatus of this type is, for example, known from German Laid-Open Publication DE-A-196 32 728 (corresponding to European Patent Application EP 0 905 025 A1). The hooping apparatus known from this document is also called a longitudinal hooping apparatus because the direction of conveyance of the packing unit to be hooped and the hooping direction of the hooping band are identical. Therefore, the packing unit is hooped in the direction of conveyance. For hooping, the packing unit is first traversed onto a working table that forms part of the apparatus, in order to then be hooped on the working table in the next step of the operation. For problem-free traversability of the packing unit onto the working table, the hooping band is mounted in a hooping frame pivotable about a longitudinal axis running in the direction of conveyance. The transporting of the packing unit onto or off of the working table is done simply in such a way that, prior to feeding and prior to removing the packing unit, the hooping frame is pivoted far enough away from the working table that it makes the working surface of the working table accessible and thus no longer stands in the way of the packing unit.
Disadvantageous in this known hooping apparatus is the fact that the entire hooping frame with its entire mass must always be completely pivoted away before each transport step. This pivoting requires a certain expenditure of time and thus acts as a bottleneck factor for the speed of the hooping apparatus.
To avoid the movement of the entire mass of the hooping frame, a hooping apparatus is known, e.g., from German Laid-Open Publication DE-A-195 03 112 (corresponding to U.S. Pat. No. 5,680,813 to Schwede), in which the hooping band is inserted and drawn taut around the packing unit simply with the aid of compressed air and with the aid of an insertion and withdrawal device. Due to the low stability of form of the hooping band the precision of guiding and positioning of the hooping band in this case is to be regarded as disadvantageous.
Finally, German Patent DE-C 41 00 276 (corresponding to U.S. Pat. No. 5,078,057 to Pearson) discloses a so-called cross hooping apparatus. This hooping apparatus has a band application frame disposed with a lateral offset with respect to the direction of conveyance. This band application frame is multiply curved and wound within itself so that it is disposed in the upper area once again more toward the middle of the working table in the direction of conveyance. With the aid of this band application frame a multiply curved and wound hooping band loop is applied. This falls to a certain extent in the direction of the goods to be hooped and is drawn taut with the aid of a retightening device. Disadvantageous in this case are the curves and windings of the hooping band forming the band loop. Particularly disadvantageous in this connection is the so-called “formation of sabers” to be found again and again in hooping bands. Therein the hooping band is twisted in its longitudinal plane because it is conducted during its production around several rollers. In the area of these rollers, the breaks in the longitudinal plane, the so-called sabers, arise at the reversing points on stretching and forming of the plastic hooping band. With curves and windings in the band-feeding channel, these sabers lead to the hooping band repeatedly becoming entangled. A further disadvantage in the case of this known cross hooping machine is the fact that the applied hooping band loop is no longer reliably guided after its release from the guide channel of the band application frame.